Spin discrete breathers in two-dimensional square anisotropic ferromagnets

We present an analytical study of spin discrete breathers in two-dimensional ferromagnets with easy-plane anisotropy by means of the coherent-state method combined with the Dyson-Maleev representation of spin operators. Making use of the semidiscrete multiple-scale method, the equation of motion for the coherent amplitude is reduced to the two-dimensional nonlinear Schrodinger equation. We show that the system can produce the two-dimensional spin discrete breathers whose eigenfrequency lies above the top of the linear spin-wave spectrum. In addition, we analyze the existence conditions of such spin discrete breathers and discuss their properties.